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Kaffir lime

life science Maturity 9-11 Next article →

The kaffir lime, scientifically known as *Citrus hystrix*, is a unique citrus plant native to tropical Southeast Asia. It is highly valued for its intense fragrance and its specific uses in cooking and industry.

Citrus hystrix Blanco2.408-cropped
Citrus hystrix Blanco2.408-cropped

People use its fruit and leaves in many Southeast Asian cuisines. Additionally, the essential oils extracted from the plant are used in perfumery and cosmetics. This plant is a significant part of the botanical and culinary landscape in many tropical regions.

Physically, *Citrus hystrix* grows as a tall, thorny shrub or a small tree. The plant is easily identified by its distinctive "double" leaves. These leaves have an hourglass shape because of a feature called a winged petiole. This is a flattened, leaf-like stalk that makes the leaf look like two pieces joined together. The fruit itself is quite small and has a very bumpy, rough exterior. It starts as a green color and eventually ripens to yellow.

Kaffir Lime (Citrus hystrix) 1
Kaffir Lime (Citrus hystrix) 1

The fruit has a thick skin, which is botanically known as the pericarp. This skin and the juice inside are both very acidic and slightly bitter.

There are many different names for this plant depending on the region. In Indonesia and Malaysia, the names refer to its "warty" or "rough-skinned" texture. In China, it is known as the "arrow-leaf lime." In Thailand, it is called *makrut*, a name also used for the bergamot orange. The plant has a complicated history regarding its primary common name. Some suggest the name comes from the Kaffirs, an ethnic group in Sri Lanka. Others suggest the name was used by Indian Muslims to denote an exotic origin. Because the term "kaffir" is an ethnic slur in South Africa, many authors now prefer the name "makrut lime" or "Thai lime" to remain neutral.

Scientific interest in the plant dates back several centuries. Pierre Sonnerat collected specimens of the plant between 1771 and 1772. Later, the plant was documented in Lamarck's *Encyclopédie Méthodique* in 1796. In 1868, texts in Ceylon referred to the plant as the kaffir lime. In Ceylon, people would rub the juice on their legs and socks to prevent leech bites. This specific use led to the plant being called "leech lime" in some historical records.

The plant's powerful scent is caused by specific chemical compounds. The leaf oil contains up to 80 percent of a compound called (–)-(S)-citronellal. This is the main substance responsible for its characteristic aroma. Other components in the leaf oil include citronellol, which makes up about 10 percent, as well as nerol and limonene. Interestingly, the leaves contain only the (S) stereoisomer of citronellal. This is different from lemon balm, which contains the (+)-(R) version. The fruit peel contains different oils, primarily limonene and β-pinene.

Culinary uses for *Citrus hystrix* are widespread across many different cultures. In Thailand, the leaves are a key ingredient in dishes like tom yum. In Cambodia, the leaves form the base of a paste called "krueng." Vietnamese cooks use the leaves to add fragrance to chicken or to reduce the odor when steaming snails. In some Vietnamese villages, silkworm pupae are stir-fried with these leaves. In the islands of Mauritius, Réunion, and Madagascar, the zest is used in creole cooking. In Cambodia, the entire fruit can even be candied for eating.

Beyond the kitchen, the plant has many medicinal and industrial applications. The juice is used in traditional medicine and can be used in shampoo to kill head lice. In Thailand and Cambodia, the juice also serves as a cleanser for hair and clothing. In Cambodia, slices of the fruit are used in lustral water for religious ceremonies. The essential oils are also used in the pharmaceutical, cosmetic, and perfume industries. However, users should be careful because the plant contains furanocoumarins. These compounds can cause phytophotodermatitis, which is a type of skin inflammation caused by sunlight.

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File:Citrus hystrix Blanco2.408-cropped.jpg
Citrus hystrix Blanco2.408-cropped.jpg
File:Kaffir Lime (Citrus hystrix) 1.jpg
Kaffir Lime (Citrus hystrix) 1.jpg
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